Control apparatus and control method

ABSTRACT

Provided is a control apparatus that controls any one or all of a plurality of slave station apparatuses communicating with a terminal apparatus, a plurality of master station apparatuses that control the slave station apparatuses, and a transfer apparatus that transfers data transmitted and received between the master station apparatuses and the slave station apparatuses, the control apparatus including an information acquisition unit that acquires information regarding traffic of the data transmitted and received between the master station apparatuses and the slave station apparatuses, and a switching control unit that performs, on the basis of the information regarding the traffic acquired by the information acquisition unit, switching-control of an assignment relationship between the master station apparatus and the slave station apparatus and switching-control of a transfer path of data between the master station apparatus and the slave station apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371of International Application No. PCT/JP2019/028409, having anInternational Filing Date of Jul. 19, 2019, which claims priority toJapanese Application Serial No. 2018-137920, filed on Jul. 23, 2018. Thedisclosure of the prior application is considered part of the disclosureof this application, and is incorporated in its entirety into thisapplication.

TECHNICAL FIELD

The present disclosure relates to a control apparatus and a controlmethod.

BACKGROUND ART

In the related art, in a wireless communication system, and particularlyin a mobile communication system, a Centralized-Radio Access Network(C-RAN) configuration in which a base station device (base stationapparatus) constituted by one device, as disclosed in, for example, NonPatent Literature 1, is divided into two devices, a master stationdevice (master station apparatus) and a slave station device (slavestation apparatus), has been examined in order to increase flexibilityin installing a base station.

FIG. 11 is a diagram illustrating a configuration of a communicationsystem 1 of C-RAN in the related art. As illustrated in FIG. 11, in theconfiguration of the communication system 1 of C-RAN in the related art,master station devices 101 (101-1 to 101-3) and slave station devices201 (201-1 to 201-3) are connected to each other on a one-to-one basis,and the plurality of master station devices 101-1 to 101-3 areaggregated at one location. For example, in FIG. 11, the master stationdevice 101-1 is connected to the slave station device 201-1, the masterstation device 101-2 is connected to the slave station device 201-2, andthe master station device 101-3 is connected to the slave station device201-3.

However, in C-RAN in the related art in which Physical (PHY) layerfunctions including a baseband signal processing function are aggregatedinto the master station device 101 to transmit IQ data of a wirelesssignal, an increase in the amount of transmission data between themaster station device 101 and the slave station device 201 has become aproblem.

Consequently, as in Non Patent Literature 2, a technique for reducingthe amount of transmission data by redefining the division of functionsof a master station device and a slave station device has been examined.Division points in the redefinition of the division of functions includea plurality of candidates. A master station device and a slave stationdevice are constituted by a Packet Data Convergence Protocol (PDCP)layer, a Radio Link Control (RLC) layer, a Media Access Control (MAC)layer, and a PHY layer.

Among the division points, a division point having a function of a PDCPlayer in a master station device and having functions of an RLC layerand layers below the RLC layer in a slave station device is referred toas a Higher Layer Split (HLS). In an HLS, the amount of transmissiondata between a master station device and a slave station device issmaller than that of C-RAN in the related art, and a delay request alsobecomes less severe.

On the other hand, function division having functions of a MAC layer andlayers above the MAC layer or functions of an upper PHY layer and layersabove the PHY layer in the master station device, and having the otherfunctions in the slave station device, is referred to as a lower layersplit (LLS). In an LLS, the amount of transmission data and a delayrequest are close to those of C-RAN in the related art, but a high basestation association performance can be maintained, which is one of theadvantages of C-RAN in the related art.

In either an HLS or an LLS, signal data between a master station deviceand a slave station device can be transmitted and received by anEthernet (trade name) frame due to the redefinition of the functiondivision. Thus, it is assumed that a transfer device (transferapparatus) such as a switch, for example, is installed between themaster station device and the slave station device. FIG. 12 is a diagramillustrating a configuration of a communication system 2 in which atransfer device is installed. In the drawing illustrated in FIG. 12, atransfer device 302 is installed between master station devices 102(102-1 to 102-3) and slave station devices 202 (202-1 to 202-3). Thetransfer device 302 is a device that transfers data transmitted andreceived between the master station devices 102 (102-1 to 102-3) and theslave station devices 202 (202-1 to 202-3). The transfer device 302 is,for example, a switch.

It is also assumed that a network is constructed by installing aplurality of transfer devices between the master station devices and theslave station devices. FIG. 13 is a diagram illustrating a configurationof a communication system 3 in which a plurality of transfer devices areinstalled. In the drawing illustrated in FIG. 13, a plurality oftransfer devices 303 (303-1 to 303-4) are installed between masterstation devices 103 (103-1 to 103-6) and slave station devices 203(203-1 to 203-6). The transfer devices 303 are devices that transferdata transmitted and received between the master station devices 103(103-1 to 103-6) and the slave station devices 203 (203-1 to 203-6). Thetransfer device 303 is, for example, a switch. Also in the cases ofFIGS. 12 and 13, the master station devices and the slave stationdevices are logically connected to each other on a one-to-one basis.

CITATION LIST Non Patent Literature

-   Non Patent Literature 1: Kohei Kiyoshima and three others,    “LTE-Advanced commercial development utilizing advanced C-RAN    architecture—Achievement of stable communication by capacity    expansion based on add-on cell and advanced inter-cell    association—,” NTT DOCOMO Technical Journal Vol. 23, No. 2, pp.    11-18-   Non Patent Literature 2: Anil Umesh and four others, “5G radio    access network standardization trend,” NTT DOCOMO Technical Journal    Vol. 25, No. 3, pp. 33-43

SUMMARY OF THE INVENTION Technical Problem

In a case where master station devices and slave station devices arelogically connected to each other on a one-to-one basis, processingresources of the master station devices will be used exclusively evenwhen the amount of traffic to be processed by the slave station devicesis small, and thus a large amount of processing resources of the masterstation devices is wasted. On the other hand, in a case where the amountof traffic of the slave station devices which are to be processed by themaster station devices is excessively large, processing resources of themaster station devices are insufficient. In this manner, in a case wherea network is constructed between the master station devices and theslave station devices, there is a problem in that processing resourcesof the master station devices cannot be effectively utilized.

In view of the above-described circumstances, an object of the presentdisclosure is to provide a technique making it possible to effectivelyutilize processing resources of a master station apparatus in a casewhere a network having a transfer apparatus disposed between the masterstation apparatus and a slave station apparatus is constructed.

Means for Solving the Problem

An aspect of the present disclosure is a control apparatus that controlsany one or all of a plurality of slave station apparatuses, a pluralityof master station apparatuses, and a transfer apparatus, a slave stationapparatus of the plurality of slave station apparatuses being assignedto a master station apparatus of the plurality of master stationapparatuses, the master station apparatus controlling the slave stationapparatus, and the transfer apparatus transferring data transmitted andreceived between the master station apparatus and the slave stationapparatus, the control apparatus including an information acquisitionunit that acquires information regarding traffic of the data transmittedand received between the master station apparatus and the slave stationapparatus, and a switching control unit that performs, on the basis ofthe information regarding the traffic acquired by the informationacquisition unit, switching-control of an assignment relationshipbetween the master station apparatus and the slave station apparatus andswitching-control of a transfer path of data between the master stationapparatus and the slave station apparatus.

In the control apparatus according to the aspect of the presentdisclosure, in a case where traffic of another slave station apparatusof the plurality of slave station apparatuses that is assigned toanother master station apparatus of the plurality of master stationapparatuses is able to be processed in one master station apparatus ofthe plurality of master station apparatuses, the switching control unitperforms switching-control of an assignment relationship to assign theother slave station apparatus assigned to the other master stationapparatus to the one master station apparatus, and performsswitching-control of a transfer path of data by instructing the otherslave station apparatus to set destinations of data transmitted from theother slave station apparatuses assigned to the other master stationapparatus to be a destination of the one master station apparatus.

In the control apparatus according to the aspect of the presentdisclosure, in a case where traffic of another slave station apparatusof the plurality of slave station apparatuses that is assigned toanother master station apparatus of the plurality of master stationapparatuses is able to be processed in one master station apparatus ofthe plurality of master station apparatuses, the switching control unitperforms switching-control of an assignment relationship to assign theother slave station apparatus assigned to the other master stationapparatus to the one master station apparatus, and performsswitching-control of a transfer path of data by instructing the transferapparatus to set destinations of data transmitted from the other slavestation apparatuses assigned to the other master station apparatus to bea destination of the one master station apparatus.

The control apparatus according to the aspect of the present disclosurefurther includes an information sharing unit that shares, with anothercontrol apparatus, information regarding any one or all of the masterstation apparatus, the slave station apparatus, and the transferapparatus that are not connected to the control apparatus, in which theswitching control unit performs the switching-control of the assignmentrelationship and the switching-control of the transfer path of data onany one apparatus of the master station apparatus, the slave stationapparatus, and the transfer apparatus that are connected to the controlapparatus, using the information shared with the other control apparatusby the information sharing unit.

In the control apparatus according to the aspect of the presentdisclosure, in a case where traffic of a plurality of slave stationapparatuses assigned to one master station apparatus of the plurality ofmaster station apparatuses is equal to or greater than a predeterminedpercentage of processing resources of the one master station apparatus,the switching control unit performs switching-control of an assignmentrelationship to assign a slave station apparatus which is a target forswitching, among the plurality of slave station apparatuses assigned tothe one master station apparatus, to another master station apparatus ofthe plurality of master station apparatuses, and performsswitching-control of a transfer path of data by instructing the slavestation apparatus which is a target for switching, among the pluralityof slave station apparatuses assigned to the one master stationapparatus, to set a destination of data transmitted from the slavestation apparatus which is a target for switching to be a destination ofthe other master station apparatus.

In the control apparatus according to the aspect of the presentdisclosure, in a case where traffic of a plurality of slave stationapparatuses assigned to one master station apparatus of the plurality ofmaster station apparatuses is equal to or greater than a predeterminedpercentage of processing resources of the one master station apparatus,the switching control unit performs switching-control of an assignmentrelationship to assign a slave station apparatus which is a target forswitching, among the plurality of slave station apparatuses assigned tothe one master station apparatus, to another master station apparatus ofthe plurality of master station apparatuses, and performsswitching-control of a transfer path of data by instructing the transferapparatus to set a destination of data transmitted from the slavestation apparatus which is a target for switching, among the pluralityof slave station apparatuses assigned to the one master stationapparatus, to be a destination of the other master station apparatus.

Another aspect of the present disclosure is a control method performedby a control apparatus that controls any one or all of a plurality ofslave station apparatuses, a plurality of master station apparatuses,and a transfer apparatus, a slave station apparatus of the plurality ofslave station apparatuses being assigned to a master station apparatusof the plurality of master station apparatuses, the master stationapparatus controlling the slave station apparatus, the transferapparatus transferring data transmitted and received between the masterstation apparatus and the slave station apparatus, the control methodincluding acquiring information regarding traffic of the datatransmitted and received between the master station apparatus and theslave station apparatus, and performing, on the basis of the informationregarding the traffic acquired in the acquiring of the information,switching-control of an assignment relationship between the masterstation apparatus and the slave station apparatus and switching-controlof a transfer path of data between the master station apparatus and theslave station apparatus.

Effects of the Invention

According to the present disclosure, it is possible to effectivelyutilize processing resources of master station apparatuses in a casewhere a network having a transfer apparatus disposed between the masterstation apparatus and a slave station apparatus is constructed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a communicationsystem according to a first embodiment.

FIG. 2 is a flowchart illustrating a flow of processing of a controldevice according to the first embodiment.

FIG. 3 is a diagram illustrating a configuration of the communicationsystem after switching control according to the first embodiment.

FIG. 4 is a diagram illustrating a configuration of a communicationsystem according to a second embodiment.

FIG. 5 is a diagram illustrating a configuration of a communicationsystem according to a third embodiment.

FIG. 6 is a diagram illustrating another configuration of thecommunication system according to the third embodiment.

FIG. 7 is a diagram illustrating a configuration of a communicationsystem according to a fourth embodiment.

FIG. 8 is a diagram illustrating a configuration of a communicationsystem according to a fifth embodiment.

FIG. 9 is a flowchart illustrating a flow of processing of a controldevice according to the fifth embodiment.

FIG. 10 is a diagram illustrating a configuration of the communicationsystem after switching control according to the fifth embodiment.

FIG. 11 is a diagram illustrating a configuration of a communicationsystem of C-RAN in the related art.

FIG. 12 is a diagram illustrating a configuration of a communicationsystem in which a transfer device is installed.

FIG. 13 is a diagram illustrating a configuration of a communicationsystem in which a plurality of transfer devices are installed.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described below withreference to the drawings.

First Embodiment

FIG. 1 is a diagram illustrating a configuration of a communicationsystem 100 according to a first embodiment. The communication system 100includes a plurality of master station devices (master stationapparatuses) 10 (10-1 to 10-6), a plurality of slave station devices(slave station apparatuses) 20 (20-1 to 20-6), a plurality of transferdevices (transfer apparatuses) 30 (30-1 to 30-4), and a control device(control apparatus) 40.

In FIG. 1, the master station devices 10-1 to 10-3 are connected to thetransfer device 30-1. The master station devices 10-4 to 10-6 areconnected to the transfer device 30-2. The slave station devices 20-1 to20-3 are connected to the transfer device 30-3. The slave stationdevices 20-4 to 20-6 are connected to the transfer device 30-4. Inaddition, the control device 40 is connected to the master stationdevices 10-1 to 10-6 and the plurality of slave station devices 20-1 to20-6.

The transfer device 30-1 is connected to the transfer device 30-2 andthe transfer device 30-3 in addition to the master station devices 10-1to 10-3. The transfer device 30-2 is connected to the transfer device30-1 and the transfer device 30-4 in addition to the master stationdevices 10-4 to 10-6. The transfer device 30-3 is connected to thetransfer device 30-1 and the transfer device 30-4 in addition to theslave station devices 20-1 to 20-3. The transfer device 30-4 isconnected to the transfer device 30-2 and the transfer device 30-3 inaddition to the slave station devices 20-4 to 20-6.

In addition, arrows 50-1 to 50-6 illustrated in FIG. 1 indicate transferpaths of data. For example, the arrow 50-1 represents a transfer path ofdata from the master station device 10-1 to the slave station device20-1 in a downlink, and a transfer path of data from the slave stationdevice 20-1 to the master station device 10-1 in an uplink.

The master station device 10 controls the slave station device 20assigned to the master station device 10. The master station devices 10and the slave station devices 20 are logically connected to each otheron a one-to-one basis. For example, the slave station device 20-1 isassigned to the master station device 10-1, the slave station device20-2 is assigned to the master station device 10-2, the slave stationdevice 20-3 is assigned to the master station device 10-3, the slavestation device 20-4 is assigned to the master station device 10-4, theslave station device 20-5 is assigned to the master station device 10-5,and the slave station device 20-6 is assigned to the master stationdevice 10-6.

The master station device 10 stores information regarding the slavestation device 20 assigned to the master station device 10. Theinformation regarding the slave station device 20 is information foridentifying the slave station device 20 and is, for example, a MACaddress of the slave station device 20, or the like. The master stationdevice 10 transmits and receives data to and from the slave stationdevice 20 assigned to the master station device 10 in a case wherecontrol is not performed by the control device 40. In a case wherecontrol is performed by the control device 40, the master station device10 changes an assignment relationship and transmits and receives data toand from the slave station device 20 instructed by the control device40.

The slave station device 20 communicates with a terminal device notillustrated in the drawing. The slave station device 20 transmits andreceives data to and from the master station device 10 to which theslave station device 20 is assigned in a case where control is notperformed by the control device 40. In a case where control is performedby the control device 40, the slave station device 20 changes anassignment relationship and transmits and receives data to and from themaster station device 10 instructed by the control device 40.

The transfer device 30 transfers data transmitted and received betweenthe master station device 10 and the slave station device 20 to adestination included in the data. The transfer device 30 is, forexample, a switch.

The control device 40 controls the master station device 10 and theslave station device 20. Specifically, the control device 40 performsswitching-control of an assignment relationship between the masterstation device 10 and the slave station device 20, and switching-controlof a transfer path of data between the master station device 10 and theslave station device 20.

Next, a functional configuration of the control device 40 will bedescribed.

The control device 40 includes a central processing unit (CPU), amemory, an auxiliary storage device, and the like connected to eachother through a bus and executes a control program. The control device40 functions as a device including an information acquisition unit 401,a switching control unit 402, and an information storage unit 403 byexecuting the control program. Note that all or some functions of thecontrol device 40 may be realized using hardware such as an applicationspecific integrated circuit (ASIC), a programmable logic device (PLD),or a field programmable gate array (FPGA). In addition, the controlprogram may be recorded in a computer-readable recording medium. Thecomputer-readable recording medium is, for example, a portable mediumsuch as a flexible disk, a magneto-optical disk, a ROM or a CD-ROM, or astorage device such as a hard disk drive built into a computer system.In addition, the control program may be transmitted and received throughan electrical communication line.

The information acquisition unit 401 acquires information regardingtraffic by monitoring traffic of data transmitted and received betweenthe master station device 10 and the slave station device 20. Theinformation regarding traffic is, for example, information of the amountof traffic. Specifically, the information acquisition unit 401 acquiresthe amount of traffic from the master station devices 10-1 to 10-6 tothe slave station devices 20-1 to 20-6 in a downlink and the amount oftraffic from the slave station devices 20-1 to 20-6 to the masterstation devices 10-1 to 10-6 in an uplink.

The switching control unit 402 performs switching-control of anassignment relationship between the master station device 10 and theslave station device 20 and switching-control of a transfer path of databetween the master station device 10 and the slave station device 20 inresponse to traffic detected by the information acquisition unit 401.

The information storage unit 403 stores information regarding a deviceto which the control device 40 is connected (hereinafter referred to as“connection device information”). For example, the information storageunit 403 stores processing resources of the master station device 10 andinformation of the slave station device 20 assigned to the masterstation device 10, for each master station device 10. In addition, forexample, the information storage unit 403 stores information of themaster station device 10 to which the slave station device 20 isassigned for each slave station device 20. The information storage unit403 is constituted using a storage device such as a magnetic hard diskdevice or a semiconductor storage device.

FIG. 2 is a flowchart illustrating a flow of processing of the controldevice 40 according to the first embodiment.

The information acquisition unit 401 acquires the amount of traffic ofeach of the master station devices 10 by monitoring traffic of datatransmitted and received between the master station device 10 and theslave station device 20 (step S101). For example, the informationacquisition unit 401 may monitor traffic output from the master stationdevice 10 to acquire the amount of traffic of each of the master stationdevices 10, or may monitor traffic input from the master station device10 to acquire the amount of traffic of each of the master stationdevices 10. The information acquisition unit 401 outputs information ofthe acquired amount of traffic to the switching control unit 402.

The switching control unit 402 determines whether there is a masterstation device 10 capable of processing the slave station device 20assigned to another master station device 10 on the basis of theinformation of the amount of traffic which is output from theinformation acquisition unit 401 and the connection device informationstored in the information storage unit 403 (step S102). Specifically,the switching control unit 402 adds the amount of traffic of the slavestation device 20 assigned to a certain master station device 10 and theamount of traffic of at least one slave station device 20 among theplurality of slave station devices 20 assigned to other master stationdevices 10, and determines that there is a master station device 10capable of processing the slave station device 20 assigned to anothermaster station device 10 in a case where the sum does not exceedprocessing resources of the master station device 10.

For example, the switching control unit 402 adds the amount of trafficof the slave station device 20-1 assigned to the master station device10-1 and the amount of traffic of the slave station device 20-2 assignedto the other master station device 10-2, and determines that there is amaster station device 10 capable of processing the slave station device20-2 assigned to the other master station device 10-2 in a case wherethe sum does not exceed processing resources of the master stationdevice 10-1.

On the other hand, in a case where the sum exceeds the processingresources of the master station device 10, it is determined that thereis no master station device 10 capable of processing the slave stationdevice 20 assigned to another master station device 10.

In a case where there is no master station device 10 capable ofprocessing the slave station device 20 assigned to another masterstation device 10 (step 102—NO), the control device 40 terminates theprocessing of FIG. 2.

On the other hand, in a case where there is a master station device 10capable of processing the slave station device 20 assigned to anothermaster station device 10 (step 102—YES), the switching control unit 402performs switching-control of an assignment relationship (step S103).Specifically, the switching control unit 402 instructs the masterstation device 10 and the slave station device 20 which are targets forswitching of an assignment relationship to switch the assignmentrelationship.

For example, in a case where the amount of traffic flowing to the slavestation devices 20-1 to 20-3 is small and capable of being processed bythe master station device 10-1, the switching control unit 402 gives aninstruction for switching an assignment relationship so that all of theslave station devices 20-1 to 20-3 are assigned to the master stationdevice 10-1. In addition, the switching control unit 402 instructs themaster station devices 10-1 to 10-3 to switch an assignment relationshipso that all of the slave station devices 20-1 to 20-3 are assigned tothe master station device 10-1. Thereby, the master station devices 10-1to 10-3 and the slave station devices 20-1 to 20-3 change their ownsetting. In this case, the master station device 10-2 cancels anassignment relationship with the slave station device 20-2, and themaster station device 10-3 cancels an assignment relationship with theslave station device 20-3. The slave station devices 20-1 to 20-3 changethe setting of the slave station devices 20-1 to 20-3 to be assigned tothe master station device 10-1. The master station device 10-1 changesthe setting of the master station device 10-1 to assign the slavestation devices 20-1 to 20-3 to the master station device 10-1.

Thereafter, the switching control unit 402 performs switching-control ofa transfer path (step S104).

Specifically, the switching control unit 402 performs switching-controlof a transfer path so that data is transmitted and received to and fromthe device after an assignment relationship is changed. For example, inthe above-described example, the switching control unit 402 switches atransfer path so that data is transmitted and received between themaster station device 10-1 and the slave station devices 20-1 to 20-3.

The switching control unit 402 performs switching-control of a transferpath by transmitting, to the master station device 10 and the slavestation device 20, an instruction for changing a destination address ofa frame to be transmitted in the master station device 10 and the slavestation device 20. For example, the switching control unit 402 transmitsan instruction for setting a destination address of data to be themaster station device 10-1 for the slave station devices 20-1 to 20-3and transmits an instruction for setting a destination address of datato be the slave station devices 20-1 to 20-3 for the master stationdevice 10-1. Thereby, the slave station devices 20-1 to 20-3 set adestination address of data to be the master station device 10-1. Inaddition, the master station device 10-1 sets a destination address ofdata to be any one of the slave station devices 20-1 to 20-3.

FIG. 3 is a diagram illustrating a configuration of the communicationsystem 100 after switching control according to the first embodiment.

As illustrated in FIG. 3, after the switching control is performed, atransfer path is switched such that data is transmitted and receivedbetween the master station device 10-1 and the slave station devices20-1 to 20-3, and control is performed such that data is not transmittedand received to and from the master station devices 10-2 and 10-3.Thereby, the master station devices 10-2 and 10-3 do not need tooperate, and processing resources are freed up.

The control device 40 configured as described above performsswitching-control of an assignment relationship between the masterstation device 10 and the slave station device 20 in accordance withtraffic of data transmitted and received between the master stationdevice 10 and the slave station device 20. In the switching-control,when traffic of the slave station devices 20 assigned to other masterstation devices 10 can be processed by one master station device 10, theslave station devices are assigned to the master station device 10capable of processing traffic of the slave station devices 20 assignedto other master station devices 10. In addition, the control device 40performs switching-control of a transfer path of data between the masterstation device 10 and the slave station device 20 afterswitching-control of an assignment relationship is performed. Thereby,processing resources of the master station device 10, of whichassignment to the slave station device 20 has been cancelled, are freedup, and the master station device 10 to which the slave station device20 assigned to another master station device 10 is newly assigned canutilize the processing resources. For this reason, in a case where anetwork is constructed between the master station device 10 and theslave station device 20, processing resources of the master stationdevice 10 can be effectively utilized.

In addition, the master station device 10, of which assignment to theslave station device 20 has been cancelled, does not need to operate.

For this reason, power consumption can also be reduced.

Modification Example

An object to be monitored by the information acquisition unit 401 may bea quality of service (QoS) value of traffic, rather than the amount oftraffic.

Second Embodiment

FIG. 4 is a diagram illustrating a configuration of a communicationsystem 100 a according to a second embodiment. The communication system100 a includes a plurality of master station devices 10 a (10 a-1 to 10a-6), a plurality of slave station devices 20 a (20 a-1 to 20 a-6), aplurality of transfer devices 30 a (30 a-1 to 30 a-4), and a controldevice 40 a. In the second embodiment, the control device 40 a isconnected to the master station devices 10 a-1 to 10 a-6, the slavestation devices 20 a-1 to 20 a-6, and the transfer devices 30 a-1 to 30a-4.

The master station device 10 a stores information regarding the slavestation device 20 a belonging to the master station device 10 a.

The master station device 10 a transmits and receives data to and fromthe slave station device 20 a which is assigned to the master stationdevice 10 a in a case where control is not performed by the controldevice 40 a. The master station device 10 a changes an assignmentrelationship in a case where control is performed by the control device40 a.

The slave station device 20 a communicates with a terminal device notillustrated in the drawing. The slave station device 20 a transmits andreceives data to and from the master station device 10 a to which theslave station device 20 a is assigned in a case where control is notperformed by the control device 40 a. In a case where control isperformed by the control device 40 a, the slave station device 20 achanges an assignment relationship.

In a case where control is not performed by the control device 40 a, thetransfer device 30 a transfers data transmitted and received between themaster station device 10 a and the slave station device 20 a to adestination included in the data. In a case where control is performedby the control device 40 a, the transfer device 30 a transfers datatransmitted and received between the master station device 10 a and theslave station device 20 a to a destination instructed by the controldevice 40 a.

In addition, the transfer device 30 a monitors traffic of datatransmitted and received between the master station device 10 a and theslave station device 20 a. For example, the transfer device 30 a-1monitors traffic of the master station devices 10 a-1 to 10 a-3, thetransfer device 30 a-2 monitors traffic of the master station devices 10a-4 to 10 a-6, the transfer device 30 a-3 monitors traffic of the slavestation devices 20 a-1 to 20 a-3, and the transfer device 30 a-4monitors traffic of the slave station devices 20 a-4 to 20 a-6. Thetransfer device 30 a transmits information of the amount of trafficacquired by monitoring to the control device 40 a. The information ofthe amount of traffic includes information for identifying the masterstation device 10 a or the slave station device 20 a and the amount oftraffic. The transfer device 30 a is, for example, a switch.

Next, a specific configuration of the control device 40 a will bedescribed.

The control device 40 a includes a CPU, a memory, an auxiliary storagedevice, and the like which are connected to each other by a bus, andexecutes a control program. The control device 40 a functions as adevice including an information acquisition unit 401 a, a switchingcontrol unit 402 a, and an information storage unit 403 by executing thecontrol program. Note that all or some functions of the control device40 a may be realized using hardware such as an ASIC, a PLD, or an FPGA.In addition, the control program may be recorded in a computer-readablerecording medium. The computer-readable recording medium is, forexample, a portable medium such as a flexible disk, a magneto-opticaldisk, a ROM or a CD-ROM, or a storage device such as a hard disk drivebuilt into a computer system. In addition, the control program may betransmitted and received through an electrical communication line.

The control device 40 a differs in configuration from the control device40 in that the information acquisition unit 401 a and the switchingcontrol unit 402 a are provided instead of the information acquisitionunit 401 and the switching control unit 402. The control device 40 a isthe same as the control device 40 for the other configurations. Thus,the information acquisition unit 401 a and the switching control unit402 a will be described.

The information acquisition unit 401 a acquires traffic of datatransmitted and received between the master station device 10 a and theslave station device 20 a from the transfer device 30 a.

The switching control unit 402 a performs the same process as that ofthe switching control unit 402. A difference between processingperformed by the switching control unit 402 a and processing performedby the switching control unit 402 is switching-control of a transferpath. Specifically, the switching control unit 402 a performsswitching-control of a transfer path on the transfer device 30 a so thatdata is transmitted and received to and from a device after anassignment relationship is changed.

Referring to FIG. 3 as an example, that is, in a case where a transferpath is switched so that data is transmitted and received between themaster station device 10 a-1 and the slave station devices 20 a-1 to 20a-3, the switching control unit 402 a transmits an instruction forchanging all destinations of data of the slave station devices 20 a-1 to20 a-3 received by the transfer device 30 a-3 for an uplink signal tothe master station device 10 a-1 to the transfer device 30 a-3. Inaddition, an instruction for changing destinations of data of the masterstation device 10 a-1 received by the transfer device 30 a-1 for adownlink signal to any one of the slave station devices 20 a-1 to 20 a-3is transmitted to the transfer device 30 a-1.

The control device 40 a configured as described above can obtain thesame effects as those in the first embodiment.

In addition, the control device 40 a performs switching-control of atransfer path of data on the transfer device 30 a that transfers databetween the master station device 10 a and the slave station device 20 ainstead of performing the switching-control on the master station device10 a and the slave station device 20 a. Thereby, even in a case wherethe number of master station devices 10 a and the number of slavestation devices 20 a, which are targets for switching-control of atransfer path of data, have increased, it is not necessary to performcontrol on all of the master station devices 10 a and the slave stationdevices 20 a which are targets for switching-control of a transfer pathof data. For this reason, it is possible to reduce a processing load ofthe control device 40 a.

Modification Example

The control device 40 a may acquire information of the amount of trafficby the information acquisition unit 401 a similar to the firstembodiment, rather than acquiring the information from the transferdevice 30 a.

An object to be monitored by the transfer device 30 a may be a QoS valueof traffic rather than the amount of traffic.

Third Embodiment

FIG. 5 is a diagram illustrating a configuration of a communicationsystem 100 b according to a third embodiment. The communication system100 b includes a plurality of master station devices 10 (10-1 to 10-6),a plurality of slave station devices 20 (20-1 to 20-6), a plurality oftransfer devices 30 (30-1 to 30-4), and a plurality of control devices40 b (40 b-1 to 40 b-4). In the third embodiment, the control device 40b is connected to the master station devices 10-1 to 10-6 and the slavestation devices 20-1 to 20-6.

More specifically, the control device 40 b-1 is connected to the masterstation devices 10-1 to 10-3, the control device 40 b-2 is connected tothe master station devices 10-4 to 10-6, the control device 40 b-3 isconnected to the slave station devices 20-1 to 20-3, and the controldevice 40 b-4 is connected to the slave station devices 20-4 to 20-6. Inthis manner, in the third embodiment, the control devices 40 b aredisposed to be distributed in plural (for example, four), and theplurality of control devices 40 b share information included in each ofthe plurality of control devices 40 b to control the master stationdevices 10 and the slave station devices 20.

Next, a functional configuration of the control device 40 b will bedescribed. Note that the control devices 40 b-1 to 40 b-4 have the sameconfiguration except that their connecting devices are different. Forthis reason, description will be given by collectively referring to thecontrol devices 40 b-1 to 40 b-4 as the control device 40 b.

The control device 40 b includes a CPU, a memory, an auxiliary storagedevice, and the like which are connected to each other by a bus, andexecutes a control program. The control device 40 b functions as adevice including an information acquisition unit 401 b, a switchingcontrol unit 402 b, an information storage unit 403 b, and aninformation sharing unit 404 b by executing the control program. Notethat all or some functions of the control device 40 a may be realizedusing hardware such as an ASIC, a PLD, or an FPGA. In addition, thecontrol program may be recorded in a computer-readable recording medium.The computer-readable recording medium is, for example, a portablemedium such as a flexible disk, a magneto-optical disk, a ROM or aCD-ROM, or a storage device such as a hard disk drive built into acomputer system. In addition, the control program may be transmitted andreceived through an electrical communication line.

The information acquisition unit 401 b acquires information regardingtraffic by monitoring traffic of data transmitted and received betweenthe master station device 10 and the slave station device 20.Specifically, the information acquisition unit 401 b acquires the amountof traffic from the master station devices 10 to the slave stationdevices 20 in a downlink and the amount of traffic from the slavestation devices 20 to the master station devices 10 in an uplink.

The switching control unit 402 b performs switching-control of anassignment relationship of either the master station device 10 or theslave station device 20 and switching-control of a transfer path of databetween the master station device 10 and the slave station device 20, inaccordance with traffic detected by the information acquisition unit 401b. Specifically, in a case where the control device 40 b is connected tothe master station device 10 and is not connected to the slave stationdevice 20, the switching control unit 402 b performs switching-controlof an assignment relationship and switching-control of a transfer pathof data on the master station device 10. Furthermore, in a case wherethe control device 40 b is connected to the slave station device 20 andis not connected to the master station device 10, the switching controlunit 402 b performs switching-control of an assignment relationship andswitching-control of a transfer path of data on the slave station device20.

The information storage unit 403 b stores connection device information.Information regarding a device (for example, the master station devices10-1 to 10-3) to which a certain control device 40 b (for example, thecontrol device 40 b-1) is connected and information regarding a device(for example, a device other than the master station devices 10-1 to10-3) to which another control device 40 b (for example, the controldevice 40 b other than the control device 40 b-1) acquired by theinformation sharing unit 404 b is connected are stored in theinformation storage unit 403 b as the connection device information.

The information sharing unit 404 b shares information with other controldevices 40 b. For example, the information sharing unit 404 b transmitsthe connection device information stored in the information storage unit403 b of the control devices 40 b to the other control devices 40 b, andshares information by receiving the connection device information fromthe other control devices 40 b. The information sharing unit 404 bstores the received connection device information in the informationstorage unit 403 b. Note that a timing at which the information sharingunit 404 b shares information may be a preset timing or may be a timingat which information of the amount of traffic is acquired.

The control device 40 b performs switching-control of an assignmentrelationship and switching-control of a transfer path of data asfollows.

Specifically, the switching control unit 402 b-1 performsswitching-control of an assignment relationship and switching-control ofa transfer path of data on the master station devices 10-1 to 10-3.

In addition, the switching control unit 402 b-2 performsswitching-control of an assignment relationship and switching-control ofa transfer path of data on the master station devices 10-4 to 10-6.

In addition, the switching control unit 402 b-3 performsswitching-control of an assignment relationship and switching-control ofa transfer path of data on the slave station devices 20-1 to 20-3.

Further, the switching control unit 402 b-4 performs switching-controlof an assignment relationship and switching-control of a transfer pathof data on the slave station devices 20-41 to 20-6.

A method of performing switching-control of an assignment relationshipand switching-control of a transfer path of data is the same as that inthe first embodiment, and thus description thereof will be omitted.

In the first embodiment, switching-control of an assignment relationshipand switching-control of a transfer path of data are performed on all ofthe master station devices 10 and the slave station devices 20 by onecontrol device 40. On the other hand, each of the plurality of controldevices 40 b configured as described above performs switching-control ofan assignment relationship and switching-control of a transfer path ofdata only on a device to which the control devices 40 b is connected.Thereby, it is possible to reduce a processing load generated in onecontrol device 40 b.

In addition, similarly to the first embodiment, in a case where anetwork is constructed between the master station device 10 and theslave station device 20, processing resources of the master stationdevice 10 can be effectively utilized.

Modification Example

An object to be monitored by the information acquisition unit 401 b maybe a QoS value of traffic rather than the amount of traffic.

Rather than sharing information between the plurality of control devices40 b-1 to 40 b-4, a high-level control device connected to the pluralityof control devices 40 b-1 to 40 b-4 may be configured to acquire allpieces of information and transmit an instruction for control to each ofthe control devices 40 b-1 to 40 b-4 on the basis of the acquiredinformation.

In the communication system 100 b of the third embodiment, the controldevice 40 b may be configured to be also connected to the transferdevice 30 as in the second embodiment. FIG. 6 is a diagram illustratinganother configuration of the communication system 100 b according to thethird embodiment. The communication system 100 b illustrated in FIG. 6includes a plurality of master station devices 10 (10-1 to 10-6), aplurality of slave station devices 20 (20-1 to 20-6), a plurality oftransfer devices 30 (30-1 to 30-4), and a plurality of control devices40 b (40 b-1 to 40 b-8). In the drawing illustrated in FIG. 6, thecontrol device 40 b is connected to the master station devices 10-1 to10-6, the slave station devices 20-1 to 20-6, and the transfer device30.

More specifically, in the drawing illustrated in FIG. 6, in addition tothe communication system 100 b in FIG. 5, the control device 40 b-5 isconnected to the transfer device 30-1, the control device 40 b-6 isconnected to the transfer device 30-2, the control device 40 b-7 isconnected to the transfer device 30-3, and the control device 40 b-8 isconnected to the transfer device 30-4. In this manner, in anotherexample of the third embodiment, the control devices 40 b are disposedto be distributed in plural (for example, eight), and the plurality ofcontrol devices 40 b share information included in each of the pluralityof control devices 40 b to control the master station devices 10, theslave station devices 20, and the transfer devices 30.

As specific processing, the third embodiment differs from the secondembodiment in that the control devices 40 b-5 to 40 b-8 are individuallyinstalled for the respective transfer devices 30-1 to 30-4, and thecontrol devices 40 b-5 to 40 b-8 perform control only on the transferdevices 30-1 to 30-4 to which each of the control devices 40 b-5 to 40b-8 is connected. Specific control processing is the same as that in thesecond embodiment, and thus description thereof will be omitted.

Fourth Embodiment

FIG. 7 is a diagram illustrating a configuration of a communicationsystem 100 c according to a fourth embodiment. The communication system100 c includes a plurality of master station devices 10 (10-1 to 10-6),a plurality of slave station devices 20 (20-1 to 20-6), a plurality oftransfer devices 30 (30-1 to 30-4), and a control device 40 c. In thefourth embodiment, the control device 40 c is connected to all of themaster station devices 10-1 to 10-6, the slave station devices 20-1 to20-6, and the transfer devices 30-1 to 30-4.

The control device 40 c executes switching-control of an assignmentrelationship and switching-control of a transfer path of data in thefirst to third embodiments in combination. For example, the controldevice 40 c may monitor the amount of traffic as in the firstembodiment, transmit an instruction for performing switching-control ofa transfer path of data to the transfer device 30 as in the secondembodiment, acquire information of the amount of traffic from thetransfer device 30 as in the second embodiment, and transmit aninstruction for performing switching-control of a transfer path of datato the master station device 10 and the slave station device 20 as inthe first embodiment. Note that, in this case, the control device 40 cmay be configured to be distributed in plural and share information asin the third embodiment, instead of as one device as illustrated in FIG.7.

Next, a functional configuration of the control device 40 c will bedescribed.

The control device 40 c includes a CPU, a memory, an auxiliary storagedevice, and the like which are connected to each other by a bus, andexecutes a control program. The control device 40 c functions as adevice including an information acquisition unit 401 c, a switchingcontrol unit 402 c, an information storage unit 403 c, and aninformation sharing unit 404 c by executing the control program. Notethat all or some functions of the control device 40 c may be realizedusing hardware such as an ASIC, a PLD, or an FPGA. In addition, thecontrol program may be recorded in a computer-readable recording medium.The computer-readable recording medium is, for example, a portablemedium such as a flexible disk, a magneto-optical disk, a ROM or aCD-ROM, or a storage device such as a hard disk drive built into acomputer system. In addition, the control program may be transmitted andreceived through an electrical communication line.

The information acquisition unit 401 c performs the same processes asthose of the information acquisition units 401, 401 a, and 401 b in thefirst to third embodiments. Note that whether to perform the sameprocessing as that of any one of the information acquisition units 401,401 a, and 401 b is appropriately set.

The switching control unit 402 c performs the same processes as those ofthe switching control units 402, 402 a, and 402 b in the first to thirdembodiments. Note that whether to perform the same processing as that ofany one of the switching control units 402, 402 a, and 402 b isappropriately set.

The information storage unit 403 c stores connection device information.

The information sharing unit 404 c performs the same processing as thatof the information sharing unit 404 b.

The control device 40 c configured as described above can obtain thesame effect as in the first to third embodiments.

In addition, the control device 40 c can perform a plurality of controlsfor switching-control of an assignment relationship andswitching-control of a transfer path of data. Thereby, the controldevice 40 c can perform more suitable control depending on thesituation. For this reason, it is possible to improve convenience.

Modification Example

The communication system 100 c according to the fourth embodiment may bemodified in the same manner as in the first to third embodiments.

Fifth Embodiment

FIG. 8 is a diagram illustrating a configuration of a communicationsystem 100 d according to a fifth embodiment. The communication system100 d includes a plurality of master station devices 10 (10-1 and 10-4to 10-6), a plurality of slave station devices 20 (20-1 to 20-6), aplurality of transfer devices 30 (30-1 to 30-4), and a control device 40d. In the fifth embodiment, the control device 40 d is connected to themaster station devices 10-1 to 10-6 and the slave station devices 20-1to 20-6.

Further, in the fifth embodiment, three slave station devices 20-1 to20-3 are assigned to the master station device 10-1, and the slavestation devices 20 are not assigned to the master station devices 10-2and 10-3. That is, the fifth embodiment is an embodiment correspondingto a case where the plurality of slave station devices 20 are assignedto one master station device 10 through the processing of any one of thefirst to fourth embodiments or a case where the plurality of slavestation devices 20 are assigned to one master station device 10 beforethe processing of the first to fourth embodiments is performed.

Next, a functional configuration of the control device 40 d will bedescribed.

The control device 40 d includes a CPU, a memory, an auxiliary storagedevice, and the like connected to each other through a bus and executesa control program. The control device 40 d functions as a deviceincluding an information acquisition unit 401, a switching control unit402 d, and an information storage unit 403 by executing the controlprogram. Note that all or some functions of the control device 40 d maybe realized using hardware such as an ASIC, a PLD, or an FPGA. Inaddition, the control program may be recorded in a computer-readablerecording medium. The computer-readable recording medium is, forexample, a portable medium such as a flexible disk, a magneto-opticaldisk, a ROM or a CD-ROM, or a storage device such as a hard disk drivebuilt into a computer system. In addition, the control program may betransmitted and received through an electrical communication line.

The control device 40 d differs in configuration from the controldevices 40, 40 a, 40 b, and 40 c according to the other embodiments inthat the control device 40 d includes the switching control unit 402 d.The control device 40 d is the same as the control devices 40, 40 a, 40b, and 40 c for the other configurations. For this reason, the switchingcontrol unit 402 d will be described.

The switching control unit 402 d performs the same processing as theswitching control unit 402. A difference between processing performed bythe switching control unit 402 d and processing performed by theswitching control unit 402 is switching-control of an assignmentrelationship.

Specifically, the switching control unit 402 d performsswitching-control of an assignment relationship on the master stationdevice 10 and the slave station device 20 so as to make the plurality ofslave station devices 20 assigned to one master station device 10 beassigned to other master station devices 10.

FIG. 9 is a flowchart illustrating a flow of processing of the controldevice 40 d according to the fifth embodiment.

The information acquisition unit 401 acquires the amount of traffic ofthe master station devices 10 by monitoring traffic of data transmittedand received between the master station devices 10 and the slave stationdevices 20 (step S201). The information acquisition unit 401 outputs theinformation of the acquired amount of traffic to the switching controlunit 402.

The switching control unit 402 d determines whether or not traffic to beprocessed by one master station device 10 exceeds processing resourcesof one master station device 10 on the basis of the information of theamount of traffic output from the information acquisition unit 401 andconnection device information stored in the information storage unit 403(step S202). Specifically, the switching control unit 402 d firstacquires processing resources of a certain master station device 10 (forexample, the master station device 10-1) with reference to theconnection device information. Next, the switching control unit 402 dcompares the acquired processing resources with the sum of the amountsof traffic of the slave station devices 20 (for example, the slavestation devices 20-1 to 20-3) belonging to a certain master stationdevice 10 (for example, the master station device 10-1).

Then, in a case where the sum of the amounts of traffic exceeds theprocessing resources, the switching control unit 402 d determines thattraffic to be processed by one master station device 10 exceedsprocessing resources of one master station device 10.

On the other hand, in a case where the sum of the amounts of trafficdoes not exceed the processing resources, the switching control unit 402d determines that traffic to be processed by one master station device10 does not exceed the processing resources of one master station device10.

In a case where traffic to be processed by one master station device 10does not exceed processing resources of one master station device 10(step 202—NO), the control device 40 d terminates the processing of FIG.9.

On the other hand, in a case where traffic to be processed by one masterstation device 10 exceeds processing resources of one master stationdevice 10 (step 202—YES), the switching control unit 402 d performsswitching-control of an assignment relationship (step S203).Specifically, the switching control unit 402 d instructs the masterstation device 10 and the slave station device 20 for which switching ofan assignment relationship is to be performed to switch an assignmentrelationship.

For example, the switching control unit 402 d instructs the masterstation device 10-1 to perform switching for cancelling the assignmentof the slave station devices 20-2 and 20-3 to the master station device10-1, instructs the slave station devices 20-2 and 20-3 to performswitching for belonging to other master station devices 10, andinstructs other master station devices 10 to perform switching for theassignment of the slave station devices 20-2 and 20-3 to the othermaster station devices 10. Here, other master station devices 10 are,for example, master station devices 10 to which other slave stationdevices 20 are not assigned or master station devices 10 having a marginof processing resources even when the slave station devices 20 areassigned to the master station devices 10.

In FIG. 9, it is assumed that the switching control unit 402 d instructsthe slave station device 20-2 to perform switching for belonging to themaster station device 10-2, instructs the slave station device 20-3 toperform switching for belonging to the master station device 10-3,instructs the master station device 10-2 to perform switching for makingthe slave station device 20-2 are assigned to the master station device10-2, and instructs the master station device 10-2 to perform switchingfor making the slave station device 20-2 are assigned to the masterstation device 10-2.

Thereby, the master station devices 10-1 to 10-3 and the slave stationdevices 20-1 to 20-3 change their own setting. In this case, the masterstation device 10-1 cancels an assignment relationship between the slavestation devices 20-2 and 20-3. In addition, the slave station device20-2 changes the setting of the slave station device 20-2 so as to beassigned to the master station device 10-2. The master station device10-2 changes the setting of the master station device 10-2 so as to makethe slave station device 20-2 be assigned to the master station device10-2. The slave station device 20-3 changes the setting of the slavestation device 20-3 so as to be assigned to the master station device10-3. The master station device 10-3 changes the setting of the masterstation device 10-3 so as to make the slave station device 20-3 beassigned to the master station device 10-3.

Thereafter, the switching control unit 402 d performs switching-controlof a transfer path (step S204). Specifically, the switching control unit402 d performs switching-control of a transfer path so that data istransmitted and received to and from a device after an assignmentrelationship is changed. For example, in the above-described example,the switching control unit 402 d switches a transfer path so that datais transmitted and received between the master station device 10-2 andthe slave station device 20-2 and between the master station device 10-3and the slave station device 20-3.

The switching control unit 402 d performs switching-control of atransfer path by transmitting, to the master station device 10 and theslave station device 20, an instruction for changing a destinationaddress of a frame to be transmitted in the master station device 10 andthe slave station device 20. For example, the switching control unit 402d transmits an instruction for setting a destination address of data tobe an address of the slave station device 20-1 to the master stationdevice 10-1. In addition, the switching control unit 402 d transmits aninstruction for setting a destination address of data to be an addressof the master station device 10-2 to the slave station device 20-2 andtransmits an instruction for setting a destination address of data to bean address of the slave station device 20-2 to the master station device10-2.

Further, the switching control unit 402 d transmits an instruction forsetting a destination address of data to be an address of the masterstation device 10-3 to the slave station device 20-3 and transmits aninstruction for setting a destination address of data to be an addressof the slave station device 20-3 to the master station device 10-3.Thereby, the slave station device 20-2 sets a destination address ofdata to be the master station device 10-2. The slave station device 20-3sets a destination address of data to be the master station device 10-3.The master station device 10-2 sets a destination address of data to bethe slave station device 20-2. The master station device 10-3 sets adestination address of data to be the slave station device 20-3.

FIG. 10 is a diagram illustrating a configuration of the communicationsystem 100 after switching control according to the fifth embodiment.

As illustrated in FIG. 10, after switching control is performed, atransfer path is switched such that data is transmitted and receivedbetween the master station device 10-1 and the slave station device20-1, between the master station device 10-2 and the slave stationdevice 20-2, and between the master station device 10-3 and the slavestation device 20-3, and control is performed such that data of theslave station device 20-2 and the slave station device 20-3 is nottransmitted and received to and from the master station device 10-1.Thereby, traffic that cannot be processed by only the master stationdevice 10-1 can be processed, and processing resources of the masterstation devices 10-1 to 10-3 can be effectively utilized.

In a case where traffic of a plurality of slave station devices 20cannot be processed by only a certain specific master station device 10under a situation where the plurality of slave station devices 20 areassigned to the specific master station device 10, the control device 40configured as described above disperses traffic by causing the slavestation devices 20 to be assigned to other master station devices 10.Thereby, all traffic can be processed, and processing resources of themaster station devices 10 can be effectively utilized.

Modification Example

An object to be monitored by the information acquisition unit 401 may bea QoS value of traffic rather than the amount of traffic.

In the process of step S202, the switching control unit 402 d may beconfigured to execute the process of step S203 and the subsequentprocesses in a case where traffic to be processed by one master stationdevice 10 exceeds a predetermined percentage (for example, 80%) ofprocessing resources of one master station device 10. With such aconfiguration, traffic can be dispersed before traffic to be processedby one master station device 10 exceeds processing resources of onemaster station device 10. Thus, it is possible to prevent traffic frombeing unable to be processed due to excess of processing resources ofone master station device 10.

In the present embodiment, as in the first embodiment, a case where thecontrol device 40 d is connected to the master station devices 10-1 to10-6 and the slave station devices 20-1 to 20-6 has been described, butthe control device 40 d may be connected to all of the master stationdevices 10-1 to 10-6, the slave station devices 20-1 to 20-6, and thetransfer devices 30-1 to 30-4 to give an instruction for performingswitching-control of a transfer path of data to the transfer device 30as in the second embodiment. In addition, switching-control of anassignment relationship and switching-control of a transfer path of datamay be performed using a method of any one of the first to fourthembodiments.

In the above-described embodiments, the numbers of the master stationdevices 10 and 10 a and the numbers of the slave station devices 20 and20 a are not necessarily limited to the above-described numbers as longas the numbers are two or more. In addition, the numbers of the transferdevices 30 and 30 a are not necessarily limited to the above-describednumbers as long as the numbers are one or more.

The embodiments of the present disclosure have been described above indetail with reference to the drawings. However, specific configurationsare not limited to those embodiments, and include any design or the likewithin the scope not departing from the gist of the present disclosure.

REFERENCE SIGNS LIST

-   10, 10-1 to 10-6, 10 a, 10 a-1 to 10 a-6 Master station device    (Master station apparatus)-   20, 20-1 to 20-6, 20 a, 20 a-1 to 20 a-6 Slave station device (Slave    station apparatus)-   30, 30-1 to 30-4, 30 a, 30 a-1 to 30 a-4 Transfer device (Transfer    apparatus)-   40, 40 a, 40 b, 40 c, 40 d Control device (Control apparatus)-   401, 401 a, 401 b, 401 b-1 to 401 b-8, 401 c Information acquisition    unit-   402, 402 a, 402 b, 402 b-1 to 402 b-8, 402 c, 402 d Switching    control unit-   403, 403 b, 403 b-1 to 403 b-8, 403 c Information storage unit-   404, 404 b, 404 b-1 to 404 b-8, 404 c Information sharing unit

The invention claimed is:
 1. A control apparatus that controls any oneor all of a plurality of slave station apparatuses, a plurality ofmaster station apparatuses, and a transfer apparatus, a slave stationapparatus of the plurality of slave station apparatuses being assignedto a master station apparatus of the plurality of master stationapparatuses, the master station apparatus controlling the slave stationapparatus, and the transfer apparatus transferring data transmitted andreceived between the master station apparatus and the slave stationapparatus, the control apparatus comprising: an informationacquisitioner configured to acquire information regarding traffic of thedata transmitted and received between the master station apparatus andthe slave station apparatus; and a switching controller configured toperform, on the basis of the information regarding the traffic acquiredby the information acquisitioner, switching-control of an assignmentrelationship between the master station apparatus and the slave stationapparatus, and switching-control of a transfer path of data between themaster station apparatus and the slave station apparatus, the controlapparatus further comprising: an information sharing unit configured toshare, with another control apparatus, information regarding any one orall of the master station apparatus, the slave station apparatus, andthe transfer apparatus that are not connected to the control apparatus,wherein the switching controller performs the switching-control of theassignment relationship and the switching-control of the transfer pathof data on any one apparatus of the master station apparatus, the slavestation apparatus, and the transfer apparatus that are connected to thecontrol apparatus, using the information shared with the other controlapparatus by the information sharing unit.
 2. The control apparatusaccording to claim 1, wherein, in a case where traffic of another slavestation apparatus of the plurality of slave station apparatuses that isassigned to another master station apparatus of the plurality of masterstation apparatuses is able to be processed in one master stationapparatus of the plurality of master station apparatuses, the switchingcontroller performs switching-control of an assignment relationship toassign the other slave station apparatus assigned to the other masterstation apparatus to the one master station apparatus, and performsswitching-control of a transfer path of data by instructing the otherslave station apparatus to set destinations of data transmitted from theother slave station apparatuses assigned to the other master stationapparatus to be a destination of the one master station apparatus. 3.The control apparatus according to claim 1, wherein, in a case wheretraffic of another slave station apparatus of the plurality of slavestation apparatuses that is assigned to another master station apparatusof the plurality of master station apparatuses is able to be processedin one master station apparatus of the plurality of master stationapparatuses, the switching controller performs switching-control of anassignment relationship to assign the other slave station apparatusassigned to the other master station apparatus to the one master stationapparatus, and performs switching-control of a transfer path of data byinstructing the transfer apparatus to set destinations of datatransmitted from the other slave station apparatuses assigned to theother master station apparatus to be a destination of the one masterstation apparatus.
 4. The control apparatus according to claim 1,wherein, in a case where traffic of a plurality of slave stationapparatuses assigned to one master station apparatus of the plurality ofmaster station apparatuses is equal to or greater than a predeterminedpercentage of processing resources of the one master station apparatus,the switching controller performs switching-control of an assignmentrelationship to assign a slave station apparatus which is a target forswitching, among the plurality of slave station apparatuses assigned tothe one master station apparatus, to another master station apparatus ofthe plurality of master station apparatuses, and performsswitching-control of a transfer path of data by instructing the slavestation apparatus which is a target for switching, among the pluralityof slave station apparatuses assigned to the one master stationapparatus, to set a destination of data transmitted from the slavestation apparatus which is a target for switching to be a destination ofthe other master station apparatus.
 5. The control apparatus accordingto claim 1, wherein, in a case where traffic of a plurality of slavestation apparatuses assigned to one master station apparatus of theplurality of master station apparatuses is equal to or greater than apredetermined percentage of processing resources of the one masterstation apparatus, the switching controller performs switching-controlof an assignment relationship to assign a slave station apparatus whichis a target for switching, among the plurality of slave stationapparatuses assigned to the one master station apparatus, to anothermaster station apparatus of the plurality of master station apparatuses,and performs switching-control of a transfer path of data by instructingthe transfer apparatus to set a destination of data transmitted from theslave station apparatus which is a target for switching, among theplurality of slave station apparatuses assigned to the one masterstation apparatus, to be a destination of the other master stationapparatus.
 6. A control method performed by a control apparatus thatcontrols any one or all of a plurality of slave station apparatuses, aplurality of master station apparatuses, and a transfer apparatus, aslave station apparatus of the plurality of slave station apparatusesbeing assigned to a master station apparatus of the plurality of masterstation apparatuses, the master station apparatus controlling the slavestation apparatus, the transfer apparatus transferring data transmittedand received between the master station apparatus and the slave stationapparatus, the control method comprising: acquiring informationregarding traffic of the data transmitted and received between themaster station apparatus and the slave station apparatus; performing, onthe basis of the information regarding the traffic acquired in theacquiring of the information, switching-control of an assignmentrelationship between the master station apparatus and the slave stationapparatus and switching-control of a transfer path of data between themaster station apparatus and the slave station apparatus; sharing, withanother control apparatus, information regarding any one or all of themaster station apparatus, the slave station apparatus, and the transferapparatus that are not connected to the control apparatus; andperforming the switching-control of the assignment relationship and theswitching-control of the transfer path of data on any one apparatus ofthe master station apparatus, the slave station apparatus, and thetransfer apparatus that are connected to the control apparatus, usingthe information shared with the other control apparatus.